1. Field
Embodiments of the present invention relate to medical methods and apparatus, and more particularly to a method and apparatus for attaching components in implants. In one embodiment, the components in an implant are attached in a manner to reduce fretting, debris, and/or material from wearing off the implant components. In one embodiment, a device includes a connection mechanism with a bore and cone interface. In one embodiment, a device includes a connection mechanism with a taper. In one embodiment, a device includes a connection mechanism with a thread. In one embodiment, a device includes a connection mechanism with a temperature differential. In various embodiments, any combination of features can used for a connection mechanism. In one embodiment, a device includes a connection mechanism between a prosthetic femoral neck implant to a prosthetic femoral head and/or prosthetic femoral stem implant in a total- or hemi-hip arthroplasty, and hip fracture fixation devices.
2. Description of the Related Art
In certain instances, failure of conventional implants can be attributed to wear between components in the implant. For example, metal on metal fretting and wear can result in debris or corrosion being released from the implant. In certain instances, failure of conventional artificial hip implants can be attributed to wear between a modular femoral neck implant with a femoral head implant. In certain instances, failure of conventional artificial hip implants can be attributed to wear between a modular femoral neck implant with a femoral stem or intramedullary rod implant. In some circumstances, metal on metal fretting and corrosion can lead to further damage. For example, in some conventional hip implants, fretting and/or crevice corrosion at the modular component junctions may occur. As loading is applied to the implant components from activities such as bearing weight, walking, and applying force at angles, relative micro-motion between the components can result in fretting, or wear of materials at pressure points at or near pivot points between the components. Conventional means of attaching a modular prosthetic neck can include tapping or hammering along the axis of a tapered connection, such as a Morse taper. Generally, conventional means of attaching components, such as the neck and stem or neck and head are difficult to align consistently and difficult to assemble using repeatable force. In some instances, conventional hip implants fail when the interface between the tapered surfaces are improperly aligned or seated, allowing rubbing, fretting, and wear resulting in the release of debris from the interface, which can result in increased blood serum metal levels, tissue inflammation, infection, pain, and/or necrosis. In some instances, these conventional designs can result in catastrophic failure. There is a need for an improved method and device for attaching components in implants. There is a need for an improved method and device for connections in implants that align the components and are able to apply controllable, reproducible force to engage the component connections. There is also a need for an improved method and device for attaching hip implants that use tapered connections, such as a femoral neck and/or stem and/or head, to other components in modular hip replacements.